PURPOSE The purpose of the study was to develop and validate a questionnaire to evaluate medical students' knowledge of, attitude towards and practice of evidence-based medicine (EBM). METHODS The participants of the study were 418 medical students enrolled in the Kyung Hee University School of Medicine in Seoul, Korea. To examine construct validity of the questionnaire, an exploratory factor analysis (EFA) was performed with 118 participants; a confirmatory factor analysis (CFA) was conducted with the remaining 281 participants. We developed 41 items with a 4-point Likert scale. An EFA was performed to verify the emergence of four dimensions of EBM competencies. The principal axis factoring method and the direct oblimin rotation method were used. To confirm construct validity, a CFA was conducted with the remaining 281 participants. To evaluate model fitness, root mean square error of approximation (RMSEA) and comparative fit index (CFI) were used as fit indices. We conducted ANOVA with Scheffe as discriminant validation, and calculated Cronbach's alpha of 4 subscales as reliability checkup. RESULTS After refinement procedure, factor analysis of the 32 items in therevised questionnaire yielded 4 factors. The Scree plot supported a 4 factor solution explaining 53.5% of the variance. The 4 components derived were: factor 1_knowledge on EBM (11 items; Cronbach's alpha=0.92); factor 2_ pursuit towards EBM (10; 0.88); factor 3_reluctance on EBM (7; 0.78); factor 4_practice of EBM (4; 0.75). The questionnaire could discriminate competence differences among 1-3 yr students. Satisfactory Cronbach's alpha scores were noted for each factor as well. CONCLUSION The EBM competency questionnaire was validated.